Vitamin kinetics

Table 3.1 shows the kinetic parameters for cell growth, rate models with or without inhibition and mass transfer coefficient calculation at various acetate concentrations in the culture media. The Monod constant value, KM, in the liquid phase depends on some parameters such as temperature, initial concentration of the carbon source, presence of trace metals, vitamin B solution, light intensity and agitation speeds. The initial acetate concentrations in the liquid phase reflected the value of the Monod constants, Kp and Kp. The average value for maximum specific growth rate (/xm) was 0.01 h. The value... 

In vitro and ex vivo studies have shown that FATPs transport LCFAs and very long-chain fatty acids (VLCFAs) but no medium-chain fatty acids, fatty acid esters, or lipid-soluble vitamins [4]. LCFA transport is inhibited by prior protease treatment. Synthetic substrates for FATPs include 14C-labeled fatty acids and the fluorescently labeled fatty acid analogue C1 -BODEP Y-Cl 2. Using the latter substrate, differences in fatty acid uptake kinetics between FATP expressing 3T3 LI adipocytes and 3T3 LI fibroblasts, which are devoid of FATPs, can be readily appreciated (Fig. 2). 

Sodium dodecyl sulfate and hydrogen dodecyl sulfate have been used as catalysts in the denitrosation iV-nitroso-iV-methyl-p-toluenesulfonamide [138]. The kinetics of condensation of benzidine and p-anisidine with p-dimethylamino-benzaldehyde was studied by spectrophotometry in the presence of micelles of sodium dodecyl sulfate, with the result that the surfactant increases the rate of reaction [188]. The kinetics of reversible complexation of Ni(II) and Fe(III) with oxalatopentaaminecobalt(III) has been investigated in aqueous micellar medium of sodium dodecyl sulfate. The reaction occurs exclusively on the micellar surface [189]. Vitamin E reacts rapidly with the peroxidized linoleic acid present in linoleic acid in micellar sodium dodecyl sulfate solutions, whereas no significant reaction occurs in ethanol solution [190]. 

FIG. 12 Principal component analysis similarity map defined by the principal components 1 and 2 for vitamin A excitation fluorescence spectral data. Sample coding L, R, and X stand for the GDL, rennet, and mixed systems, respectively the digits are for the time elapsed since the beginning of the kinetics. 

The ITIES with an adsorbed monolayer of surfactant has been studied as a model system of the interface between microphases in a bicontinuous microemulsion [39]. This latter system has important applications in electrochemical synthesis and catalysis [88-92]. Quantitative measurements of the kinetics of electrochemical processes in microemulsions are difficult to perform directly, due to uncertainties in the area over which the organic and aqueous reactants contact. The SECM feedback mode allowed the rate of catalytic reduction of tra 5-l,2-dibromocyclohexane in benzonitrile by the Co(I) form of vitamin B12, generated electrochemically in an aqueous phase to be measured as a function of interfacial potential drop and adsorbed surfactants [39]. It was found that the reaction at the ITIES could not be interpreted as a simple second-order process. In the absence of surfactant at the ITIES the overall rate of the interfacial reaction was virtually independent of the potential drop across the interface and a similar rate constant was obtained when a cationic surfactant (didodecyldimethylammonium bromide) was adsorbed at the ITIES. In contrast a threefold decrease in the rate constant was observed when an anionic surfactant (dihexadecyl phosphate) was used. 

From this sort of data it can be concluded that the cobalt(III) ion in this complex is a soft, or class b, Lewis acid. It has been suggested previously that the cobalt(III) ion in vitamin B12 was also a class b acid (138). The kinetic order, which presumably corresponds closely to the order of thermodynamic stability, suggests that for at least some ligands jr-bonding may be important. In this connection it is noteworthy that methylcobaloxime forms a complex with CO (139). 

M. F., The effect of water-soluble vitamin E on cyclosporine kinetics in healthy volunteers, Clin. Pharm. Ther. 1996, 59, 297-303. 

Odriozola-Serrano I, Soliva-Fortuny R, Gimeno-Ano V and Martin-Belloso O. 2008a. Kinetic study of anthocyanins, vitamin C, and antioxidant capacity in strawberry juices treated by high-intensity pulsed electric fields. J Agric Food Chem 56 8387-8393. 

The enzyme mediating remethylation, 5-methyltetrahy-drofolate-betaine methyltransferase (Fig. 40-4 reaction 4), utilizes methylcobalamin as a cofactor. The kinetics of the reaction favor remethylation. Faulty remethylation can occur secondary to (1) dietary factors, e.g. vitamin B12 deficiency (2) a congenital absence of the apoenzyme (3) a congenital inability to convert folate or B12 to the methylated, metabolically active form (see below) or (4) the presence of a metabolic inhibitor, e.g. an antifolate agent that is used in an antineoplastic regimen. 

Thiamine (vitamin B,) in the presence of Me2T10H (435). Here the kinetics are much affected, through coordination of TIMeJ to the sulfur of the thiamine in its enethiolate form. 

Thermal treatment, applied to honey, may destroy vitamins and bionutrients, and produce a simultaneous decrease in diastase activity and an increase in HMF content. Honey treatment temperature and time must be limited when pasteurising and stabilising it both diastase activity and HMF content are national and international parameters used as controls so as to limit thermal treatment application. HMF can be formed by hexose dehydration in acid media or by the Maillaid reaction [11,12]. According to Ibarz et al., HMF formation can be described by a second order kinetics (auto-catalytic), with the following equation as expression model [13] ... 

However, in the reaction of vitamin BjjS with primary halides and with benzyl chloride, where the 8 2 driving force can be calculated from the standard potential of the Co(ii)/Co(i) couple and from existing Co—C bond energy data, it appears that recasting the kinetic data point against DF Sf 2) instead of DF ET) brings it close to the ET line (Walder, 1989). 

Boso, R.L., Bellini, M.S., Miksik, I., Deyl, Z. (1995). Microemulsion electro-kinetic chromatography with different organic modifiers separation of water-and lipid-soluble vitamins. J. Chromatogr. A 709 11-20. 

Abrams, S. A., Griffin, I. J., Hawthorne, K. M., Chen, Z., Gunn, S. K., Wilde, M., Darlington, G., Shypailo, R. J., and Ellis, K. J. (2005a). Vitamin D receptor Fokl polymorphisms affect calcium absorption, kinetics, and bone mineralization rates during puberty. JBMR 20, 945-953. 

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